During the day, you can use the sun position as a reference (like it's done using a sextan). You only need an accurate clock, and can determine the sun's locati

During the day, you can use the sun position as a reference (like it's done using a sextan). You only need an accurate clock, and can determine the sun's location through the clouds. I suppose you can also do it with the moon. On a dark, cloudy night though? You could risk using the sonar since the launch is going to make a ruckus anyway. Compare measures against seafloor maps.